C14 has a long half-life for only 120 cm. I have had good results with Pb210 in peat soils. See my citations.

Also, check out Quan Hua's work using 14C for the recent past, excellent paper chock full of useful ideas and methods:

Hua, Q. Radiocarbon: A chronological tool for the recent past. Quat Geochronol 2009, 4, 378–390.

I've used this paper to great affect on ~450 year old cacti.

Find the pdf here:

https://www.researchgate.net/publication/222416034_Radiocarbon_A_chronological_tool_for_the_recent_past

Article Radiocarbon: A chronological tool for the recent past

One date is good for prospective work ("how old is this core, maybe?"), but might get you in trouble with reviewers if you try to publish ("this core is x-years old"). I would go for 4 dates at the very least...that way you can assess accumulation rate differences or reversals. Not my direct line of work, maybe others have a better recommendation?

Many thanks Nathana and Laxrence for your answers.

I will read those papers and try to take advantage of them.

You need at least 2 C14 dates, to precise if the top core is modern (or not) and to point depths hiatus.

You can contact Maarteen Blaauw (Belfast) he's specialized on age-depth modelling

Hi Mustapha. It all depends on the age you expect to have at the bottom of the core. I used to have up to 2000years in 1m of peat. We are even working a 3-m core which is 40kyrs...

So, 3-4 14C date range finders along the core would be nice, then you can refine it with more dates for specific intervals where you want to have a precise timing of events for the proxies you are investigating. And 210Pb is definitely a plus. Check Mires and Peat volume 7 for an overview of peat protocols and dating. Good luck.

Thank you so much François and Michelle for your time.

I am expecting an age between 1K and 2K years for this core, I was considering the 210Pb but thought it would be useless in my case (a virgin mountenous site without human intervention).

i will keep you informed

Yep, then I would go for at least 3-4 radiocarbon dates, and 210 Pb as the latter would give you a date for the youngest end-member of your age-depth model. Try CLAM for age modeling. Relatively user-friendly.

Salam Alikom evry one

What about two 14C (AMS) coupled with Additional delta 13C measurement (IRMS), would it be enough?

I agree that at least 3-4 are needed. I'm afraid that 2 dates are not enough, in case you want to say something about deposition rates. If you wish only to date the bottom, it's another story. By the way, it it's a site without human intervention, what are you going to date?

Leydet Michelle offers a good start, Mustapha. The obvious first dates to obtain are the bottom and the top of the core - this will tell you the span of time over which the peat was accumulating. 120 cm of peat can be a geologic instant, or if it is compacted, can be thousands of years (still a relatively short geologic time, but getting to the boundaries of the radiocarbon scale). There is a chance that the age of the bottom of the core will be too old to use 14C (about 55,000 14C y)- in which case you'll need to search for a datable portion somewhere else in the core. I don't know the geological context. But ultimately, you will want to have at least 3 meaningful dates to estimate an accumulation rate of the peat, and then you should check with Martin Blaauw's work on how to better utilize the dates for chronology of the core.

I thank you Dr Regev and Dr Rosenheim for your interest in my issue.

I am working on a peat sediment and my intention is to date peat so that I can try the reconstruction of the regional vegetation and climate history and I want to support it by 14C dating. I can't confirm about the human intervention, the site is virgin (in a mountainous region, no roads or houses nearby) but there are limited grazing activities.

I will go for 3 dates...I thank you all for your help.

What do you think of delta 13C measurement by IRMS, would it be interesting in my case? what would you chose:

3 AMS or 3 AMS + delta 13C?

Hi Mustapha,

All 14C dates should be corrected for fractionation using a d13C value for the same sample. Some laboratories providing the 14C date will measure a concurrent d13C value in the AMS, but this is not comparable to irms d13C numbers, generally. Others will measure it externally on an irms. The bottom line is that the d13C measurement is important for the 14C measurement and you can decide how it is measured by asking the proper questions at the time you submit the samples for 14C measurements.

d13C irms values are much more easily and inexpensively measured and you will find some interest in employing a laboratory with EA-irms capabilities to measure many more samples than just 3 from your core. You will also achieve %C, %N, and C:N ratios for one price in most laboratories, and it is about a factor of 10-15 less expensive than 14C measurements. These measurements can give you a start on determining the type of environment contributing C to the peat deposit and any shifts in contributions from marine and terrestrial sources. There is a plethora of papers on this from all kinds of deposits, including peat.

All of the above assumes no disturbance and unidirectional accumulation of the peat. 120cm near the surface could have been turned by a plow, so it is up to you to judge the degree of disturbance of this sample or it will be a lot of money and, more importantly, time wasted. Grazing would have a small effect at the top of the core (older than expected ages, perhaps), but not as large as other agricultural activity. It would be worth a thorough check of local land use history, unless the 120cm of peat is quite deep in the core.

In my opinion, it is not appropriate to establish the number of samples for dating based on the thickness of the peat. This decision should be determined by the, a priori, resolution of the core. You can have a thin core but high resolution, either because it is very young, or because for a particular period had a high rate of accumulation, but can also have a thin core because biogeographic conditions during the history of this generated low rates of peat accumulation.

Although, the knowledge of the paleoenvironmental evolution of the area can provide criteria for the decision, a useful strategy would be to select the samples in two steps. First, half of the dating provided uniformly distributed in the core and then, determine the remaining samples to date from the results of the initial dating.

Other criteria to be taken into account, is the target of the investigation. If the goal is to establish a general pattern, it is necessary to distribute the samples across the core to obtain general information about its evolution. If the goal is focused on a specific event, such as the medieval warm period, then it is necessary to focus more on dating in this section, although in this case first you need to make a dating that let you know the core section where you locate this period.

In general, North Atlantic Hemisphere peatlands, a age - depth model acceptable for this thickness would consist of a minimum of 10 dating. A high-resolution model should be at least 20 .

Some time ago palynologists used to do one C14 dating at the bottom, than infer the ages for the rest of the profile based on vegetation reconstructions. But for an age/depth model today, I agree with what was said above. Good luck!

Hi,

Firstly, I think you should be making an evaluation about the age extent for sediments’ deposited in the core. If the age on the bottom is less than two hundred, I think using the 14c to decide the age is not useful. I suggestion you test the Pb210 for the sediments. If the age about or more than one millennium and less than 40 millenniums, I think that it is appropriate using the 14c to decide the age-depth model. Any away, I do not know that what your research aim is. So if you want get more detail suggestion, I think that you need to give me more information about your research.

Good luck,

Bing Song

Salamo Alikom

I thank you all again for your priceless suggestions.

My study area is located in the N-E of Algeria at 1002 m Alt. As I said, I am dealing with a 120 cm peat core in terms of :

Fossil pollen

Fossil Testate Amoebae

Microscopic charcoal

The objectives of the work is to try the reconstruction of the vegetation, the hydrology and the fire history in the region. According to similar works in the same area and under the same Geological context, the age of 1 peat core is about 1 K year.

I think I will go for 3 AMS.

Hi,

I am very interesting for your research. In the fact, I have the same research experience. If all sediments in your core are peats, and have not disturb by human activities, and also don not have obviously hiatus, I think the research materiel is very good. If you have enough financial support, you should be test more than 10 14c age data, because the 14 c age resolution is about decade. If the subsample resolution is 1 cm, then you will be got 120 subsamples. Identification test all the subsample and the decade age framework, you will get good research resulted.

All of them decided by your core quality, schedule and your financial support, If the sediment in your core is very continuous, I think that it is deserve to spend more time to identification and more money to test 14c. And if you do not have enough financial support, it is also easy to application financial support from other.

Best wishes,

Bing Song

Thank you Mr Song

There is allays a balance between the cost of the 14C analysis and the importance of your research. The age dept model gets better as you have more calibrated ages. It is a good practice to sample the core once, even if you will not use all the samples for 14C analysis. Then select couple of samples 3-4 for 14C. You need a 14C age for the deepest part, maybe one from above the bottom (10-20 cm) if the bottom is contaminated. Keep in mind that in most cases, the bottom part is compressed then the upper part, so as you go deeper the age will be compressed too. Based on the results, you can decide later if you need some additional 14C analysis.

We measured delta13C values in cave guano deposit (Check out my RG profile), and we had some 14C measurements on the core, but in case of guano, the age dept model is not working because, there is no continuous guano deposition. Good luck, Feri

Thank you so much Mr Fernec, I found you answer very interesting.

In my case, the upper part of the core ( up to 30 cm) is contaminated with recent material, I will try to date parts which are deeper than 0.3 m.

What make you believe that the upper 30cm is contaminated? The upper part can be modern (after 1955) or older. If you get some modern age, that data can also be calibrated.